Epsilon Tauri
Epsilon Tauri or ε Tauri, formally named Ain (/ˈeɪn/), is an orange giant star located approximately 146 light-years (45 parsecs) from the Sun in the constellation of Taurus. An exoplanet (designated Epsilon Tauri b, later named Amateru) is believed to be orbiting the star.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Taurus |
| Right ascension | 04h 28m 37.0003s |
| Declination | +19° 10′ 49.563″ |
| Apparent magnitude (V) | +3.53 |
| Characteristics | |
| Spectral type | K0III |
| B−V color index | 1.014 |
| Astrometry | |
| Radial velocity (Rv) | 38.420±0.0004 km/s |
| Proper motion (μ) | RA: 107.526±0.193 mas/yr Dec.: −36.200±0.126 mas/yr |
| Parallax (π) | 22.3654 ± 0.1721 mas |
| Distance | 146 ± 1 ly (44.7 ± 0.3 pc) |
| Absolute magnitude (MV) | 0.145 |
| Details | |
| Mass | 2.57+0.17 −0.25 M☉ |
| Radius | 12.35+0.41 −0.36 R☉ |
| Luminosity | 78.11+5.68 −5.82 L☉ |
| Surface gravity (log g) | 2.66+0.03 −0.05 cgs |
| Temperature | 4,950±22 K |
| Metallicity [Fe/H] | +0.15±0.02 dex |
| Rotation | 141.1 days |
| Rotational velocity (v sin i) | 3.0 km/s |
| Age | 625 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
It is a member of the Hyades open cluster. As such its age is well constrained at 625 million years. It is claimed to be the heaviest among planet-harboring stars with reliable initial masses. Given its large mass, this star, though presently of spectral type K0 III, was formerly of spectral type A that has now evolved off the main sequence into the giant phase. It is regarded as a red clump giant; that is, a core-helium burning star.
Since Epsilon Tauri lies near the plane of the ecliptic, it is sometimes occulted by the Moon and (very rarely) by planets.
It has an 11th magnitude companion 182 arcseconds from the primary, although this is an unrelated background star.